CVE-2022-31021: ursa — Exploit & Fix

Description

Ursa is a cryptographic library for use with blockchains. A weakness in the Hyperledger AnonCreds specification that is not mitigated in the Ursa and AnonCreds implementations is that the Issuer does not publish a key correctness proof demonstrating that a generated private key is sufficient to meet the unlinkability guarantees of AnonCreds. The Ursa and AnonCreds CL-Signatures implementations always generate a sufficient private key. A malicious issuer could in theory create a custom CL Signature implementation (derived from the Ursa or AnonCreds CL-Signatures implementations) that uses weakened private keys such that presentations from holders could be shared by verifiers to the issuer who could determine the holder to which the credential was issued. This vulnerability could impact holders of AnonCreds credentials implemented using the CL-signature scheme in the Ursa and AnonCreds implementations of CL Signatures. The ursa project has has moved to end-of-life status and no fix is expected.

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CVSS v3.1 Score

3.3

LOW

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Weakness Type (CWE)

CWE-829 CWE-829

Affected Products

Vendor	Product	Versions
hyperledger	ursa	< 0.3

References

Advisories & Patches

https://github.com/hyperledger/ursa/security/advisories/GHSA-2q6j-gqc4-4gw3 https://github.com/hyperledger/ursa/security/advisories/GHSA-2q6j-gqc4-4gw3

Exploits

https://www.brics.dk/RS/98/29/BRICS-RS-98-29.pdf https://www.brics.dk/RS/98/29/BRICS-RS-98-29.pdf

Frequently Asked Questions

What is CVE-2022-31021? +

Ursa is a cryptographic library for use with blockchains. A weakness in the Hyperledger AnonCreds specification that is not mitigated in the Ursa and AnonCreds implementations is that the Issuer does not publish a key correctness proof demonstrating that a generated private key is sufficient to meet the unlinkability guarantees of AnonCreds. The Ursa and AnonCreds CL-Signatures implementations always generate a sufficient private key. A malicious issuer could in theory create a custom CL Signature implementation (derived from the Ursa or AnonCreds CL-Signatures implementations) that uses weakened private keys such that presentations from holders could be shared by verifiers to the issuer who could determine the holder to which the credential was issued. This vulnerability could impact holders of AnonCreds credentials implemented using the CL-signature scheme in the Ursa and AnonCreds implementations of CL Signatures. The ursa project has has moved to end-of-life status and no fix is expected. It has a CVSS v3.1 base score of 3.3 (LOW).

How severe is CVE-2022-31021? +

CVE-2022-31021 has a CVSS v3.1 score of 3.3 out of 10, rated LOW. This is a low-severity vulnerability with limited impact.

What products are affected by CVE-2022-31021? +

CVE-2022-31021 affects products from hyperledger, specifically: ursa. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2022-31021? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2022-31021